This invention relates to fire-retardant intumescent laminate systems suitable for application to combustible or heat-sensitive substrates to protect such substrate from fire and heat. More particularly this invention relates to flexible, intumescent laminate systems useful as a protective overlay for a variety of combustible or heat-deformable substrates such as wood, plywood, fiber board or organic foams.
It is well known that intumescent coatings are useful fire-retardant coatings for protection of combustible, as well as heat-sensitive, substrates. The characteristic feature of all intumescent coatings in that the intumescent composition, upon exposure to heat or flame, swells or puffs up to a relatively thick cellular foam char which possesses heat-insulative and fire-retardant properties. The heat or flame activated reaction causes the intumescent materials to foam and expand into thick cellular foam char and generate inert gases such as nitrogen, carbon dioxide, etc., which are entrapped in the foam and thus prevent the access of air and oxygen to the combustible substrate. This swelled cellular, generally carbonaceous, char layer which adheres to the substrate expands to many times the thickness of the original coating and thus effectively insulates the substrate from heat and serves as an effective oxygen barrier.
Prior art intumescent coatings have been applied as films, i.e., paints or mastic coatings, directly to the surface to be protected in liquid form by brushing, rolling or spraying. Generally, pretreatment of this surface is necessary prior to application of the intumescent coatings, and several coatings are usually required in order to achieve the necessary fire-retardant protection. Similarly, it is difficult to obtain uniform coatings. These procedures are time consuming and expensive. Furthermore, inexpensive and simple intumescent formulations cannot be used in paints because they are soluble in water. Since these intumescent coatings are usually subjected to frequent washing and high humidity conditions, the water soluble components are leached out and the coating loses most of its fire-retardant properties. Generally it has been necessary to vary intumescent formulation components in ways that increase price, oftentimes decrease intumescent behavior and/or decrease the flexibility of the intumescent paint.
Although fire-retardant tapes have been used as substitutes for prior art intumescent paints, these tapes nevertheless require the bonding of a separate intumescent coating to a backing material. As in the case of paints, involved procedures are required in order to obtain a desired uniform thickness of coating; additionally, this intumescent coating remains unprotected from the effect of solvents, particularly water if a water soluble intumescent composition is used, and wear.
On the other hand, fire-retardant sandwich panels for use as a construction material have been prepared by treating a paper with foam-forming fireproofing agent and bonding this paper to two outer layers of plastic, wood or metal. However, these outer layers are rigid and thus prevent the formation of a sufficiently thick intumescent char having the necessary heat-insulative and fire-retardant properties.
As a result of this invention, fire-retardant intumescent laminate materials have been developed which to not possess the undesirable features of the aforementioned prior art material.
An object of this invention is to provide inexpensive and effective intumescent laminate systems which possess excellent resistance to high humidity and washing conditions.
A further object is to provide flexible fire-retardant intumescent laminate systems having various thicknesses which can be easily adhered to the surface of a combustible or heat-sensitive or heat-deformable material.
Still another object is to provide and intumescent laminate system composed of multiple layers which is suitable for protection of thermally delicate organic polymeric foams.
Accordingly, the aforementioned and other objects are achieved by utilizing the fire-retardant, intumescent laminate system of this invention which comprises an intumescent layer comprising a porous sheet material which is impregnated with an intumescent composition and a flexible protective layer adhered to the outer surface of the intumescent layer. The intumescent laminates can be adhered to the surface to be protected by means of an adhesive.
The intumescent laminate systems of this invention may also include additional layers such as a vapor transmission barrier layer, e.g., aluminum foil and/or a thermal barrier layer, e.g., glass wool or cardboard adjacent to the intumescent layer. These multiple layer containing intumescent laminate systems are particularly suitable for application to the surface of highly heat-sensitive substrates such as organic foams which have relatively poor thermal stability.